By Olivia Rosane, EcoWatch.
Yet another study has shown that glaciers in Antarctica are melting at accelerating rates.
Almost 25 percent of the West Antarctic ice shelf is now thinning, and the Pine Island and Thwaites glaciers are losing ice at five times the rate they were in the early 1990s, CNN reported.
“In parts of Antarctica, the ice sheet has thinned by extraordinary amounts,” study lead author and Leeds University Prof. Andy Shepherd told The Guardian.
The study, published in Geophysical Research Letters, comes four months after another study of the entire Antarctic continent found that it was losing ice at six times the rate it was 40 years ago. The latest study found that ice loss from both East and West Antarctica had raised global sea levels by 4.6 millimeters since 1992, according to CNN.
The study relied on 25 years of satellite data covering 1992 to 2017. The satellites were fitted with altimeters to measure height changes to the ice sheets. Researchers then used weather models to separate seasonal variation due to snow fall from melting and ice loss caused by long term climate change, BBC News explained.
“Using this unique dataset, we’ve been able to identify the parts of Antarctica that are undergoing rapid, sustained thinning ― regions that are changing faster than we would expect due to normal weather patterns,” co-head of the UK Centre for Polar Observation and Modelling (CPOM) and Lancaster University Environmental Sensing Reader Dr. Malcolm McMillan told BBC News. “We can now clearly see how these regions have expanded through time, spreading inland across some of the most vulnerable parts of West Antarctica, which is critical for understanding the ice sheet’s contribution to global sea level rise.”
That understanding is showing a contribution at the high end of projections. Shepherd told BBC News that the south pole’s contribution to sea level rise by 2100 was likely to be 10 centimeters (approximately four inches) higher than the five centimeters (approximately two inches) predicted by the Intergovernmental Panel on Climate Change (IPCC).
“There is a 3,000km (approximately 1,850-mile) section of coastline ― including the Bellingshausen, Amundsen and Marie Byrd Land sections ― that is clearly not properly modelled because that’s where all the ice is coming from, and more ice than was expected,” he told BBC News.
The major driver of ice loss is warm water that melts the glaciers where they hit the sea bed, The Guardian explained. The glaciers then slide faster into the ocean and grow thinner. In some places, glaciers lost more than 100 meters (approximately 1,640 feet) of thickness. The thinning is also spreading inwards: in some places, thinning had reached 300 miles into 600 mile ice streams.
“More than 50% of the Pine Island and Thwaites glacier basins have been affected by thinning in the past 25 years. We are past halfway and that is a worry,” Shepherd told The Guardian.
If all the ice in West Antarctica were to melt, it would raise sea levels about five meters, enough to flood many coastal cities. If East Antarctica also melted, seas would rise 60 meters (approximately 197 feet).
Main image: A close-up view of the rift separating Antarctica’s Pine Island Glacier and iceberg B-46, as seen on an Operation IceBridge flight on November 7, 2018. Credit: NASA/Brooke Medley, public domain
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Falling oxygen levels caused by global warming could be a greater threat to the survival of life on planet Earth than flooding, according to researchers from the University of Leicester.
A study led by Sergei Petrovskii, Professor in Applied Mathematics from the University of Leicester’s Department of Mathematics, has shown that an increase in the water temperature of the world’s oceans of around six degrees Celsius — which some scientists predict could occur as soon as 2100 — could stop oxygen production by phytoplankton by disrupting the process of photosynthesis.
Professor Petrovskii explained: “Global warming has been a focus of attention of science and politics for about two decades now. A lot has been said about its expected disastrous consequences; perhaps the most notorious is the global flooding that may result from melting of Antarctic ice if the warming exceeds a few degrees compared to the pre-industrial level. However, it now appears that this is probably not the biggest danger that the warming can cause to the humanity.
“About two-thirds of the planet’s total atmospheric oxygen is produced by ocean phytoplankton — and therefore cessation would result in the depletion of atmospheric oxygen on a global scale. This would likely result in the mass mortality of animals and humans.”
The team developed a new model of oxygen production in the ocean that takes into account basic interactions in the plankton community, such as oxygen production in photosynthesis, oxygen consumption because of plankton breathing and zooplankton feeding on phytoplankton.
While mainstream research often focuses on the CO2 cycle, as carbon dioxide is the agent mainly responsible for global warming, few researchers have explored the effects of global warming on oxygen production.
The 2015 United Nations Climate Change Conference will be held in Le Bourget, Paris, from November 30 to December 11. It will be the 21st yearly session of the Conference of the Parties to the 1992 United Nations Framework Convention on Climate Change (UNFCCC) and the 11th session of the Meeting of the Parties to the 1997 Kyoto Protocol. The conference objective is to achieve a legally binding and universal agreement on climate, from all the nations of the world.
Yadigar Sekerci, Sergei Petrovskii. Mathematical Modelling of Plankton–Oxygen Dynamics Under the Climate Change. Bulletin of Mathematical Biology, 2015; DOI: 10.1007/s11538-015-0126-0
Changes in ocean circulation and water temperature both critically influence which phytoplankton live and which die, says Oscar Schofield, oceanography professor at Rutgers University. “It also changes how much phytoplankton and what type. The conditions of the ocean might favor a particular toxic species, and that causes it to grow,” he says. Known colloquially as “red tides,” these harmful algal blooms have been known to devastate fisheries along the Pacific and Atlantic coasts.
But as devastating as climate change and harmful blooms can be, the news isn’t all bad for marine life, Schofield says. “At Palmer Station, there’s been a decline in the Adélie penguin population by an order of magnitude,” he says. “But sub-polar penguins that live in the Falkland Islands—those populations are increasing. Species have a lot of unknown capacities for adaptation. They can evolve and change their characteristics—but it happens slowly.”
The question is, Schofield says, whether organisms can adapt in time with the climate change to ensure their survival. For phytoplankton, marine life, and humans alike, that remains to be seen.
Spinning masses of water on the surface of the ocean, called eddies, can create downward vortices. They could act like “ocean elevators,” carrying carbon-containing particles into the depths. If so, the ocean could absorb more carbon dioxide, a greenhouse gas that is warming our planet. (False-color image from Landsat-8 on Aug. 11, 2015)Rainforests have been dubbed the Earth’s lung, but like us, our planet has two lungs. The second one is the ocean. Rainforests and oceans both draw in carbon dioxide from the atmosphere, reducing the buildup of heat-trapping gas that is warming our climate. Both use photosynthetic plants to capture carbon dioxide from the atmosphere and convert it into organic carbon that the plants use to grow. But while one of these lungs relies on large trees that grow slowly over decades, the other involves microscopic organisms capable of surviving no more than a few weeks every year. Two very different pathways, producing essentially the same result: regulating the amount of carbon dioxide in Earth’s atmosphere.
The tiny organisms in the ocean are called phytoplankton. Do not let their short life expectancy and small size fool you. Though they are no wider than a human hair, phytoplankton serve the same purpose as the giant kapok trees found in the Amazon. And there are billions and billions of them. Think of it as crowdsourcing: If every phytoplankter captures even a little bit of carbon dioxide, the total effect can be very large.
Nearly 25 percent of the carbon dioxide in our atmosphere is “pumped” into the ocean, where it converted into organic carbon by phytoplankton at the ocean surface all over the world. But a lot remains unknown about the fate of this carbon once it has penetrated into the ocean. Some of it goes up the food chain, some of it dissolves into the ocean, some of it is released back to the atmosphere, and some of it sinks into deeper parts of the ocean. This last pathway is especially interesting. If the carbon sinks deep enough, it potentially could remain in the ocean for thousands of years. This one-way ticket is a promising way to efficiently “bury” carbon deep down and keep it from returning to the atmosphere.
This process is often called “carbon sequestration,” and scientists have traditionally thought that it is achieved when particles—dead organisms or fecal pellets, for example—are large and heavy enough to sink out of the ocean surface to greater depths. Smaller and lighter particles, despite being far more numerous, generally float near the surface, being stirred around by ocean currents until they decompose. Scientists have therefore assumed that these smaller particles don’t contribute to carbon sequestration into the ocean.
But what if they did? What if they contributed quite a lot?
Underwater fireworks
You can think about what happens in the ocean as fireworks. After they explode, a few large shining sparks fall all the way down, while most of the smaller sparks fade away before they get a chance to reach the ground. In the ocean, when conditions are right, the phytoplankton population explodes, creating a large number of particles of all sizes. Heavier particles sink fast enough to transport the carbon they contain to greater depths before they biodegrade. On the other hand, lighter particles disappear before they get a chance to sink deep enough.
Well, to be honest, this is only mostly true. This paradigm has been widely accepted for the main reason that ocean currents travel mainly in the horizontal direction. Generally, it’s harder for water to move up and down, and so far less water moves vertically, and when it does, it moves very slowly—about a hundred times slower than a garden snail’s top speed!
However, scientists have recently discovered that, through complex processes and in very localized regions, vertical currents do exist, and they can be much larger than we originally had thought and measured. We were missing them up to now. Why? Because those stronger vertical currents are too localized to be seen from satellites and too ephemeral to be measured consistently by oceanographers at sea.
What goes down must come up
More and more, the scientific community agrees that this water moving vertically in the ocean can act as an elevator capable of carrying light particles from the surface to greater depths, including particles that would otherwise be too light to sink on their own. Though these smaller particles each contain less carbon than larger ones, these particles are far more numerous and therefore could significantly contribute to transferring carbon from the surface to deeper depths.
This has shaken our understanding of how the ocean can regulate the amount of carbon dioxide in the atmosphere, as well as our capability to predict how the ocean will respond to the ever-increasing buildup of carbon dioxide in the atmosphere. These vertical elevators suggest that we have been underestimating how much carbon dioxide these previously disregarded smaller particles can contribute to removing carbon from the atmosphere and sequestrating it in deeper layers of the ocean.
To improve our understanding of this phenomenon, we must address many unanswered questions. How and where do these elevators form in the ocean? What happens to particles as they are moving down? How fast do those vertical elevators have to move to ensure that even small particles make it deep into the ocean before they biodegrade? Can we quantify how much more carbon sinks when those vertical elevators are present, compared with when they are absent?
This is where things get even more complicated. In the ocean, what goes down must come up—meaning that if some water is taking an elevator down, some equal amount of water must be taking another elevator up to compensate. And these going-up elevators would contain a hard-to-distinguish mixture of both larger and smaller particles.
We now have two competing mechanisms for carbon sequestration: When these vertical oceanic elevators are not present, larger particles (sparser but high in carbon) all sink deep down, and smaller particles (much more numerous but low in carbon) are all biodegraded and never make it to the deep ocean. In places where the elevators are active, many more smaller particles are sent to the deep ocean, but some larger particles are sent back up, so fewer make it down.
So what is the net effect? Are those elevators really enhancing the total amount of carbon exported into the deep ocean? And, most importantly, how can we figure it out?
Observational challenges
Because vertical currents are both localized and short-lived, it is difficult to observe them directly in the ocean. It’s also a great challenge to measure and assess the sizes and distribution of all the particles in the water.
NASA has recently put together an impressive expedition to make field observations of particles sinking and try to correlate them with satellite observations of the surface ocean. The program is called EXPORTS (Export Processes in the Ocean from Remote Sensing), and it involves scientists from many institutions, including Woods Hole Oceanographic Institution.
Meanwhile, a team of scientists at WHOI—including me, Amala Mahadevan, and David Nicholson—has been using a numerical ocean model. This advanced computer program aims to reproduce properties of the real ocean (currents, temperature, salinity, etc.) as well as processes, including those that form vertical currents. In the comfort of our offices, we can add in imaginary particles with different sizes and sinking speeds and see what happens to them as time passes. Our three main questions are:
When, where, and why do larger vertical currents occur in the ocean?
How do these vertical currents interact with particles of all sizes in the ocean?
Do vertical currents enhance or reduce the amount of carbon sequestered into the deeper parts of the ocean?
Our preliminary results have revealed that horizontal and vertical ocean currents are closely linked. In regions where horizontal currents are very strong, the water flow tends to become unstable, creating swirls of spinning waters at the currents’ peripheries. Those swirls, spinning downward like underwater hurricanes, generate vertical currents in the ocean. Think of the swirling water that appears above the drain hole in your bathtub.
Our computer model was able to recreate those swirls. Then we added particles to the model to see what happens. Our computer simulations revealed that the vertical currents are indeed very efficient at exporting small particles to the deep ocean. Not only did they transport a large amount of small particles downward, they also moved them much more rapidly than we had anticipated. Does this increased export of small particles to the deep have a greater net impact after accounting for the resurfacing of large particles? That is something our team is still actively working to resolve.
These insights, if confirmed, would significantly change our understanding of the ocean’s role in regulating carbon dioxide in the atmosphere. We may have been underestimating it. Over the past few decades, we have gained a good understanding of the oceanic lung in the Earth’s respiratory system. Our attention now has to zoom down to the level of “oceanic alveoli”—those smaller features that might very well play a fundamental and heretofore overlooked role in our climate system.
This research was funded by the National Aeronautics and Space Administration.
Because they need light, phytoplankton live near the surface, where enough sunlight can penetrate to power photosynthesis. The thickness of this layer of the ocean—the euphotic zone—varies depending on water clarity, but is at most limited to the top 200 to 300 meters (600 to 900 feet), out of an average ocean depth of 4,000 meters (13,000 feet).
Phytoplankton comprise two very different kinds of organisms. The larger category include, single-celled algae known as protists—advanced eukaryotic cells, similar to protozoans. These forms include diatoms and are most abundant near coasts. Occasionally, these organisms form blooms—rapid population explosions—in response to changing seasons and the availability of nutrients such as nitrogen, iron, and phosphorus.
The other type of phytoplankton cells, more primitive but far more abundant than algae, is photosynthetic bacteria. These tiny cells, some only a micron across, are invisible but present in numbers of hundreds of thousands of cells per tablespoon of ocean water. Too small to be caught in any net, these organisms were unknown until the 1970s, when improved technology made them visible. Scientists now know these bacteria are responsible for half of the ocean’s primary productivity and are the most abundant organisms in the sea. The group also includes cyanobacteria, which are believed to be among the oldest organisms on Earth and the origin of the photosynthetic organelles in plant cells known as chloroplasts.
Why are they important?
Phytoplankton are some of Earth’s most critical organisms and so it is vital study and understand them. They generate about half the atmosphere’s oxygen, as much per year as all land plants. Phytoplankton also form the base of virtually every ocean food web. In short, they make most other ocean life possible.
Through photosynthesis these organisms transform inorganic carbon in the atmosphere and in seawater into organic compounds, making them an essential part of Earth’s carbon cycle. Because they take up carbon dioxide from the atmosphere, when they die they sink they carry this atmospheric carbon to the deep sea, making phytoplankton an important actor in the climate system. Phytoplankton growth is often limited by the scarcity of iron in the ocean. As a result, many people are discussing plans to fertilize large areas of the ocean with iron to promote phytoplankton blooms that would transfer more carbon from the atmosphere to the deep sea.
Phytoplankton are critical to other ocean biogeochemical cycles, as well. They take up, transform, and recycle elements needed by other organisms, and help cycle elements between species in the ocean. Photosynthetic bacteria are especially important in the nutrient-poor open ocean, where they scavenge and release scarce vitamins and other micronutrients that help sustain other marine life.
Some phytoplankton have a direct impact humans and other animals. Dense blooms of some organisms can deplete oxygen in coastal waters, causing fish and shellfish to suffocate. Other species produce toxins that cause can cause illness or death among humans and even whales that are either exposed to the toxins or eat shellfish that accumulate toxins. Such harmful algal blooms (HABs) cause significant economic loss every year in the seafood industry and in tourist communities, and scientists are working to understand the causes of these blooms and to devise ways to predict and prevent them.
Jonkers, L. et al. (2019) Global change drives modern plankton communities away from the pre-industrial state, Nature, https://www.nature.com/articles/s41586-019-1230-3
Communities of zooplankton – microscopic drifting animals that underpin marine ecosystems – are migrating poleward in response to climate change, a study finds.
By comparing ancient sediment cores to modern-day plankton distribution data, the research concludes that zooplankton communities across the globe have shifted by an average of 602km since pre-industrial times.
The findings, published in Nature, show that “marine ecosystems have entered the Anthropocene”, the lead author tells Carbon Brief.
The global shift in zooplankton populations could have knock-on impacts for the marine life that feed on them, ranging from “fish to whales”, another scientist tells Carbon Brief.
Drifters
From jellyfish to baleen whales, a huge variety of marine life feeds on plankton. “Plankton” is a catch-all term referring to tiny organisms that float in water. The research paper focuses on “zooplankton” or animal plankton, as opposed to “phytoplankton” (plant plankton).
Zooplankton is made up of microscopic, often single-celled organisms, as well as the eggs and larvae of larger animals, such as krill, jellyfish and crabs.
For the study, the researchers compare the distribution of zooplankton communities in the modern day to those in the pre-industrial era.
To gather data from pre-industrial times, the researchers took sediment samples from the first centimetre of the seabed in different sites across the world.
Planktonic foraminifera assemblage from Caribbean sediments. Source: Michal Kucera
The study focused on a group of zooplankton known as foraminifera – which have hard outer shells that can stay preserved in sediment for centuries, explains lead author Dr Lukas Jonkers, a postdoctoral researcher from the University of Bremen. He tells Carbon Brief:
“To get an idea of the modern species communities, we used sediment traps. Sediment traps are big funnels – they’re about two metres high – and they are attached to the sea floor. They intercept everything that falls from the surface ocean so, in that sense, you get a very good picture of what should be below in the sediment.”
Recovery of a sediment trap on board the research vessel Meteor in the tropical North Atlantic Ocean. Source: Christiane Schmidt
The map below shows the location of the sediment traps (white dots) and the points at which ancient sediment samples were taken (grey dots). The map also shows sea surface temperature change between 1870 and 2015, with red indicating rise and blue indicating decline.
The distribution of modern-day (white dots) and ancient (grey dots) zooplankton data used in the study. Sea surface temperature change from 1870 to 2015 is also shown. Source: Jonkers et al. (2019)
Shifting seafood
The results show that modern-day zooplankton communities differ from those in the nearest ancient sediment site and that the “degree of dissimilarity scales with temperature change”, the authors write in their research paper:
“This suggests planktonic foraminifera communities have changed considerably since the pre-industrial period and that they have done so to the magnitude of local temperature change.”
This is illustrated on the chart below, which shows the relationship between sea surface temperature change and the degree of dissimilarity between modern-day and pre-industrial plankton communities at a single site.
The relationship between sea surface temperature change and the degree of dissimilarity between modern-day and pre-industrial plankton communities. Source: Jonkers et al. (2019)
The authors also found that most modern-day plankton communities were more similar to ancient samples found further away – suggesting that communities had shifted their location over time.
By comparing pre-industrial and modern-day plankton samples, they calculated that the average community had shifted 602km poleward from pre-industrial times to today. However, the degree of displacement ranged from 45 to 2,557km – dependent on the degree of sea surface temperature change.
In the northern hemisphere, it was found that plankton communities had shifted northwards in response to warming, Jonkers says:
“We’re not seeing new species or new species compositions, we’re just seeing that the same species have moved with temperature change. In most cases, this is caused by warming – because almost everywhere in the ocean is warming. But in some cases, the ocean is cooling – then we see a shift towards colder communities.”
(Ocean cooling in some regions is driven by natural changes to the climate system.)
New era
The shift in plankton communities towards the poles could be a harbinger of how ocean warming is impacting marine ecosystems, Jonkers says:
“We think that these findings are indicative of what is happening in marine ecosystems. If you take that assumption, it means that most species have moved their distribution.”
However, while some species that feed on zooplankton will be able to follow it to cooler waters, others may not be able to adapt to these new conditions, he says:
“Conditions may be different. For example, if you move north, you will face a longer summer season, so the light conditions may be different. All ecological networks will need to be reestablished, and we don’t know if all the species can do so and if they can do so quick enough.”
The findings suggest that the world’s oceans have entered the “Anthropocene”, he adds:
“Marine ecosystems have entered the Anthropocene. The changes that we are seeing are now big enough that we can say that these communities are different than before human influence.”
The research “builds upon known information” to “make a global statement”, says Dr Todd O’Brien, a zooplankton researcher from the National Oceanic and Atmospheric Administration (NOAA), who was not involved in the study. He tells Carbon Brief:
“In some ocean regions, we are seeing that some fish – and even whales – are also shifting further north, perhaps following their food or trying to stay in their preferred water temperatures, or a mixture of both.”
